1. Field of the Invention
This invention relates to a high reflection mirror designed to exploit the characteristic features of metal film. More specifically, it relates to a high reflection mirror comprising a minimal number of films and showing an excellent adhesiveness and a good corrosion-resistance that can be manufactured with a high productivity and suitably used for a sophisticated optical device such as a camera, a copying machine or a printer.
2. Related Background Art
Japanese Patent Application Laid-Open No. 2-109003 discloses a reflection mirror of the type under consideration comprising a substrate, an intermediary layer of a metal oxide formed on the substrate, a metal reflection film laid on the intermediary layer and, if necessary, a protection film laid on the metal reflection film. If the protection film is made to increase reflection, not less than six layers of a material having a low refractive index and a material showing a high refractive index have to be laid, which leads to a long film forming process and a low productivity. Additionally, it has been proved by durability tests and other tests that such a reflection increasing arrangement can reduce the reflectance and some of its layers can peel off and become suspended, degrading the film, due to the intertwined complex internal stresses of the multilayer film.
Additionally, while the use of silicon oxide or magnesium fluoride is proposed for the low refractive index material, such compounds are not without problems from the viewpoint of durability and stability of the formed film.
Meanwhile, Japanese Patent Application Laid-Open No. 11-64612 discloses a reflection mirror realized by inserting an SiO2 layer between the base layer and the Ag layer. Japanese Patent Application Laid-Open No. 52-40348 discloses a reflection mirror realized by inserting an SiO layer between a plastic substrate and a metal film. However, the adhesion of an Ag layer and an SiO2 layer and that of an Ag layer and an SiO layer are not particularly good and long constant-temperature-humidity tests have also proved that, when an reflection increasing layer having a large internal stress is laid on an Ag layer, it can peel off and become suspended, or cracks can appear.
In view of these circumstances, it is therefore an object of the present invention to dissolve the above identified problems of the prior art by providing a high reflection mirror that shows a high reflectance and an excellent corrosion-resistance as well as a good adhesiveness relative to a glass substrate and a plastic substrate and can be manufactured with a reduced total number of films to improve the productivity.
According to the invention, the above object is achieved by providing a high reflection mirror comprising:
a substrate;
a TiOx layer formed on the substrate, where 1xe2x89xa6xxe2x89xa62;
an Ag layer formed on the TiOx layer;
an Al2O3 layer formed on the Ag layer; and
a TiO2 layer formed on the Al2O3 layer.
In another aspect of the invention, there is provided a high reflection mirror comprising:
a substrate;
a SiOx layer formed on the substrate, where 1xe2x89xa6xxe2x89xa62;
a Cr layer formed on the SiOx layer;
an Ag layer formed on the Cr layer;
an Al2O3 layer formed on the Ag layer; and
a TiO2 layer formed on the Al2O3 layer.